This invention relates to molten metal processing systems and more particularly to a coupling system for use in molten metal processing systems. There are several different types of molten metal processing systems, such as pumps, degassing unites, and flux injection devices, all of which are well known in the art.
In many of these systems, a shaft is used to transmit rotation from a motor or other drive system or device to an impeller, rotor or other system component. In the molten metal pump application, this coupling device provides an operational attachment of the top part of the shaft to the drive system or motor. In prior art designs, a straight threaded design is utilized such that one external thread is machined into the external surface of the top portion of the graphite shaft and a corresponding internal thread is provided in a coupling mechanism, which is then attached or operationally attached to the motor drive system. The shaft is then rotated into the coupling by typically turning it at least one revolution, until it is securely fastened to the coupling. Long continuous corresponding threads are more cumbersome to rotate together and tend to have a relatively high failure rate.
In other prior art systems, a vertical channel, an elbow and an approximately horizontal channel are cut into the shaft, and corresponding protrusions or bumps within the inner or internal cavity of the coupling system slide up into the vertical channel and then over in the horizontal channel. However these systems are not believed as reliable as a system which includes a partial thread for greater engagement area between the shaft and the coupling, such as provided by this invention.
Molten metal may be one of the more difficult environments in which to maintain a pump or a coupling system, due to the heat and corrosive factors within the molten metal. The submerged components of these pumps and coupling systems are typically made of graphite, ceramics or similar materials due to the ability of these types of material compositions to withstand the heat and corrosive effects of the molten metal environment. If there is a failure of the shaft such as the shaft breaking, it is necessary to remove the stub within the coupling with a chisel and hammer, which causes additional potential problems with the coupling.
It is an object of aspects of this invention to provide an improved coupling system for use in coupling or attaching a molten metal shaft to another component.
It is also an object of embodiments of this invention to provide a way to remove the stub once an end of the shaft has broken off within the coupling.